The present invention concerns a device for provoking an avalanche consisting of a gas gun with its upstream end attached to a seating anchored solidly to the mountain and with its downstream end supported by at least one leg such that the mouth of the gun is located above the snow cover.
Devices for provoking avalanches are known in the art, consisting of a gas gun affixed to the side of a mountain with its base solidly anchored in a seating consisting of a concrete block and with its mouth located above the snow cover, as described in U.S. Pat. No. 5,107,765. These guns are designed to provoke avalanches in exposed areas, for example, above ski stations or inhabited areas. The devices are very effective in provoking avalanches in zones known as avalanche corridors, that is, areas consisting primarily of steeply sloped gorges where snow accumulates rapidly and may attain unstable critical masses. They have proven particularly effective on light snow that is not dense and has a high volume of air trapped inside the snow crystals. The movement triggered by detonation provokes a wave effect with strong initial compression, followed by a slower movement that breaks up the snow cover and raises the mass of snow enough to provoke an avalanche. For this reason, the mouth of the gun must be located above the snow cover.
These devices must be rigidly and very solidly anchored to the side of the mountain, specifically, by using a concrete base anchored to rock and forming the rear seating for the gun itself. To support the front portion, near the mouth of the gun, the device has one or more legs also solidly anchored to the mountain.
When the gun is shot, the force exerted on the front region reaches 80 or 160 tons, depending upon the model, and a very strong anchor is required to counteract the forces which tend to dislodge the legs.
Anchors such as these are very expensive and are only resistant if the soil holding them is stable and resistant. In shifting, unstable terrain that lacks resistance, the legs supporting the mouth of the gun tend to become dislodged and pulled out of place with each successive firing. Since the devices are generally installed in locations that are difficult to reach and even dangerous, repairs are expensive and complicated.
The present invention proposes overcoming these disadvantages by offering an effective solution to the problems described above, a solution which also lowers installation costs and significantly increases the longevity of the apparatus.
This goal is accomplished by the device wherein the upstream end of the gun is attached to the base with an articulation and in that the downstream end is ballasted, with the leg freely positioned in a seat attached to the ground.
According to a variation of the invention, the downstream end of the gun is ballasted with at least one type ballast near the mouth.
The ballast may consist of a container of granular material or concrete introduced through an opening in said container.
According to a second variation, the downstream end of the gun has at least one form of ballast inside the leg supporting it.
This leg is preferably hollow and filled with granular material or concrete.
In all embodiments, the leg is essentially vertical; it rests freely in a seating rigidly anchored to the side of the mountain and it is joined to the gun with an articulation having a horizontal axle.
Preferably the device has an ignition means near the upstream end of the gun.
The ignition means preferably consists of a sparkplug connected to an ignition system comprising a pressure controller with a dual state microbreaker, a condenser, an electric battery, and an igniter, the microbreaker providing communication between the condenser and the igniter when it is in the first state and providing communication between the condenser and the battery when in the second state.
The device may also include a safety wire connecting the seating and the leg.
The device preferably has a stop pin disposed vertically in the seat supporting the leg, said supporting seat being made of concrete and comprising a steel base covered by a rubber plate to cushion the impact of the leg.